1. Field of the Invention
The present disclosure is directed to a backlight unit and a liquid crystal display having the backlight unit.
2. Description of the Related Art
A liquid crystal display includes a backlight unit, a driving circuit unit and a liquid crystal panel. The backlight unit supplies light to the liquid crystal panel and the driving circuit unit drives the liquid crystal panel. The liquid crystal panel includes liquid crystal cells aligned in the form of a matrix. Light transmittance of each liquid crystal cell varies depending on voltage applied to the liquid crystal cell. That is, the liquid crystal display adjusts the light transmittance of the liquid crystal cell by using the driving circuit and supplies light to the liquid crystal cell by using the backlight unit, thereby displaying images.
Image signals displayed on the liquid crystal panel are sequentially scanned in the row direction. That is, the image signals are scanned from the upper portion to the lower portion of the liquid crystal panel. The scanning method is employed in the backlight unit to reduce motion blur. Similarly to the liquid crystal panel, the backlight unit is scanned in the row direction.
Since the image signals and the backlight unit are scanned, there are liquid crystal cells that are charged, that is, are subject to an applied voltage, when the backlight unit is in the ON state. If light is supplied to such liquid crystal cells from the backlight unit, capacitance of the liquid crystal cells is changed, causing leakage current. That is, a light transmittance of liquid crystal cells, which are charged when the backlight unit is in the ON state, is different from that of liquid crystal cells, which are charged when the backlight unit is in the OFF state. Such difference in light transmittance causes a difference in brightness of images displayed on the liquid crystal panel. Since the liquid crystal cells are charged in a unit of a row, a brightness difference occurs between rows. Such brightness difference causes a waterfall in the liquid crystal panel.